A filter centrifuge of the above type is described, for example, in "Knott, Systematik in der Konstruktion von Maschien und Apparaten fur die chemische Industrie, Konstruktion 1967, Vol. 6, pages 217 to 222, FIG. 5".
This filter centrifuge has its process chamber closed at a cover at the axial end of the centrifuge. The access to the process chamber and thus to the centrifuge drum is through the opening which is closed by this cover. Maintenance work on the centrifuge drum is thus carried out within the process chamber. More substantial work may require removing the centrifuge drum to a work shop and for that purpose the centrifuge drum is generally pulled out of the machine through the process chamber of the centrifuge.
For the removal of the centrifuge drum special tools may be required and these tools may be available at the sides of the opening affording access to the process chamber. If work is required on the bearings or the seals of the centrifuge drum, the centrifuge drum also must be pulled out of the machine and frequently the bearings and seals must be withdrawn as well. All of these steps require work within the process chamber of the machine which can cause cross-contamination with the materials processed in the centrifuge, whether this is contamination by the personnel of the product or contamination of the personnel by the product, contact of personnel with product residues in the process chamber or contact of the bearings or components of the bearing system with such product residues. Further, the product itself can be contaminated by lubricants and other contaminants during the disassembly process as the bearings and shaft are withdrawn through the process chamber. The problem is most pronounced in filter centrifuges in the fine chemical and pharmaceutical industries.
There are filter centrifuges which are used in conjunction with clean rooms as described, for example, in EP 0 379 452. Even here substantially all of the work required on the centrifuge must be carried out in the clean room in which the process housing is located with the danger of contamination of the clean room. During this maintenance, production is interrupted.
There are also known filter centrifuges in which the main shaft together with the bearings and seals form a unit, i.e. a so-called cartridge, together with a self-supporting bearing housing. These bearing units can be mounted independently from the remainder of the filter centrifuge and, when maintenance is required on the seals or bearings, the cartridge can be completely removed and the work performed in a work shop without the danger of contaminating the process space. The removal of the cartridge can be effected either through the process chamber or rearwardly from the process chamber. In practice, however, when disassembly of the apparatus is required, e.g. for removal of the cartridge, some work must be performed in the process chamber of the centrifuge, risking a danger of contamination by or of personnel. Furthermore, when work must be performed on the centrifuge drum, this must be done within the process chamber with all of the drawbacks previously described.
Filter centrifuges are also known in which the bearing unit can be removed together with the drum as a unit. The removal of this unit, however, also must take place through the process chamber or require work in the process chamber with the described drawbacks of cross contamination.